The present invention relates to a switching device, and more particularly to a switching device capable of handling signal having a large swing.
In a wireless communication system, e.g., an FM (Frequency Modulation) transceiver, both the receiver and the transmitter of the FM transceiver share the same antenna. Therefore, when the wireless communication system is under operation, a switch is controlled to switch between the receiver and the transmitter to couple either the receiver or the transmitter to the antenna. According to one conventional wireless communication system, the switch is installed in series with the receiver instead of the transmitter since the distortion and out-of-band emission of the transmitter is more stringent than the linearity of the receiver. For this example, when the switch is turned ON (i.e. short) under the receiving mode, the switch should have the characteristic of low insertion loss, large input range, low distortion, low die area, and etc. When the switch is turned OFF (i.e. open) under the transmitting mode, the switch should have the characteristic of capable of handling large swing signal, providing low distortion in its OFF state, not disrupting the normal transmitting operation or function of the transmitter, and etc. However, due to the circuit complexity of both the receiver and the transmitter, it is very difficult to accomplish the above-mentioned characteristic in the switch without having to drastically reduce the maximum allowable input RF (Radio Frequency) signal to the receiver and/or the maximum transmitted output power. Therefore, providing a switch that meets the above-mentioned requirements to switch between the receiver and the transmitter in the wireless communication system has become an important issue in this field.